Preparation and treatment of liquid samples by solid phase extraction is a known process whereby liquid samples are cleaned by removing targeted substances from the samples prior to chromatographic analysis. Generally, the process involves eluting the liquid samples through a solid adsorptive packing material, which solid packing usually consists of a silica-based material in bead or powder form. The elution may be more readily accomplished under the influence of a vacuum which draws the liquid samples through the solid packing material. In this manner, targeted contaminants or substances may be selectively removed from the liquid samples.
It is known in the art to construct a manifold device capable of eluting multiple liquid samples through solid packing material simultaneously. In a prior art device of this type, a vacuum chamber is provided whereby the vacuum acts to simultaneously elute a plurality (i.e., more than one) of samples. The vacuum chamber, which in the prior art has generally been constructed of either stainless steel or an opaque plastic material, is provided with a plurality of fittings in the lid or cover. The fittings may be used directly to support and drain a reagent tube, or may have had interposed in the flow path a stopcock-controlled valve. The reagent tubes consist of packed columns containing said silica material, and having a leuer connection to be placed into each of the valve fittings and supported thereby on the lid of the vacuum chamber. Liquid samples poured into the reagent tubes pass through the packed columns and are drawn through the silica material by the vacuum force into the vacuum manifold. Test tubes or other collection vessels are provided in the vacuum chamber to collect the eluent from each of the valves.
Transparent material, such as clear plastic, has been used for the housing for the vacuum chamber, so that the operator can observe the collection of eluent in the test tubes inside the chamber to monitor the progress of the sample preparation.
To the extent that vacuum manifolds known in the prior art have been provided with control valves, they have been difficult to use because they have relied on conventional stopcocks. In particular, when a plurality of reagent tubes are in place on the manifold, stopcocks have proved to be a cumbersome means of regulating the flow of the liquid samples. During a multiple extraction process, stopcock-type valves may be difficult to reach and provide an awkward means of manipulation.